Arrangement in a breathing device



Jan. 1, 1963 D. JOHANNISSON ETAL 3,07 3

ARRANGEMENT IN A BREATHING DEVICE Filed April 27. 1959 INVENTOR 0.46 JOHANN/SSO/V v HAKAN L/NDERHOLM ATTORNEY United States The present invention refers to an arrangement in a breathing device for applying breathing gas to a patient. The principal object of the arrangement is to assure that the application of breathing gas during a certain time interval remains constant and independent of possible Variations in the resistance presented by the patients breathing organs or other passages of the device, whereby the ventilation of the patient retains a constant, adjustable value.

In previously employed devices for artificial respiration, it has been possible to adjust the breathing rate, ie the number of inhalations and exhalations per minute, as well as the quantity of gas delivered by the device for each inhalation. However, such devices do not take into account the fact that the resistance presented by the patients breathing organs as Well as of the conduits connecting the device with the patient may be variable. Therefore, if for instance the resistance of the patients breathing organs increased, this resulted in an increased compression of the gas in the device and in the conduit for supplying the gas to the patient. In a case where the volume of the patients lungs is relatively small, for instance if the patient is a child, this may result in the application of an insufficient quantity of gas to the patients lungs, which means that the ventilation is unsatisfactory.

In the breathing device forming the object of the present invention, these disadvantages are obviated with the aid of means provided in the device and responsive to the pressure in a conduit for connection with the patient to control the application of breathing gas in such a way that the quantity of gas supplied to the patient per minute remains constant, whereby the ventilation of the patient remains unvariable and independent of possible pressure variations in the conduit for connection with the patient.

This result can be obtained by providing that for each inhalation, a quantity of gas is forced into the conduit for connection with the patient in dependence upon the pressure Within the said conduit, the ratio between the inhalation and exhalation times being preferably constant. It is also possible to achieve constant ventilation of the patient by varying in dependence upon the pressure within the said conduit the ratio between inhalation and exhalation time in such a way, for instance, that for an increased resistance in the patients breathing organs, the inhalation takes place during a proportionately longer time.

The invention is described in the following with reference to annexed drawing, in which FIGURE 1 shows a simplified diagram of a device according to the invention. FIG. 2 shows a modification of a detail of the FIGURE 1 device.

In FIGURE 1, reference 1 designates a patient to whom breathing gas is to be supplied. The gas may be air or oxygen, possibly with an admixture of a narcotic gas, such as laughing gas. The breathing gas is supplied through a conduit 2, in which there is inserted a nonreturn valve 3. The gas leaving the patient is led through a conduit 4, in which a small amount of underpressure may be present so as to provide some suction of the breathing gas from the patient during the exhalation. A membrane valve is inserted in the conduits 2 and 4 of such construction that one of these conduits is closed when the other is open. To this end, the membrane valve is provided with a membrane 6, which may abut either "ice against a valve seat 7 indicated in the figure or against a valve seat 8. The membrane is further actuated by a spring 9, which presses the membrane lightly against the valve seat 7. When the pressure in the conduit 2 in front of'the membrane valve 5 rises sufiiciently, membrane 6 is raised from the valve seat 7 and breathing gas is applied to the patient 1 at the same time as the conduit 4 is held closed. After the subsequent pressure drop in the said portion of the conduit 2, the membrane 6 is returned to the valve seat 7 and the patient can breathe out through the conduit 4.

The rhythmical application of breathing gas to the patient is obtained in the FIGURE 1 embodiment of the invention with the aid of a pulsator 10. It contains a membrane 11, which may influence two mechanically interconnected valves 12 and 13, for instance by means of a lever arrangement 14, in such a way that one valve is closed when the other is open. The valve 13 is inserted in a conduit 15 for applying pressure gas to the patient. When the valve 13 is open, the pressure gas flows on to a conduit 16 and further onwards through, among other things, a non-return valve 17 and an adjustable flow control screw 18 to a pressure chamber 19 on the other side of the membrane 11. Thus, when the gas flows through the non-return valve and passes the constriction 18 at a rate determined by the aperture at the constriction, the pressure rises in the chamber 19 so as to actuate the membrane 11 to close the valve 13. This simultaneously opens the valve 12, so that the conduit 16 is connected through this valve with the surrounding atmosphere. The pressure in the chamber 19 then gradually falls, owing to the fact that the gas in this chamber is returned to the conduit 16 through a conduit comprising a second constriction 2t and a non-return valve 21. When the pressure in the chamber 19 has decreased to a predetermined value, the membrane 11 is returned by a spring 22 to its original position, thereby reopening the valve 13, closing the valve 12 and repeating the sequence just described. In this manner, a periodical application .of pressure gas to the conduit 16 is obtained.

It is preferable that the ration between inhalation and exhalation time is constant and independent of possible variations in the breathing frequency. This will ensure that the ventilation in terms of litres per minute remains unchanged, even if the breathing frequency should vary. For instance, the device may be adjusted so as to make the exhalation time twice as long as the inhalation time. If then the breathing frequency is adjusted to a value of twenty per minute, this implies that each inhalation will last for one second and each exhalation for two seconds. This manner of keeping a constant ratio between inhalation and exhalation time independently of the breathing frequency results in an operation such that for a certain longer interval of time, such as one minute, there is always an unchanging fraction of the time utilized for applying breathing gas to the patient. In the example 7 chosen, this implies that there is applied to the patient in each minute breathing gas during 20 seconds.

In the embodiment of the invention shown in FIGURE 1, this constant ratio is obtained owing to the fact that the two adjustment knobs 23 and 23a for adjusting the constrictions 18 and 20 are provided with corresponding graduations arranged in such a way that the desired constant ratio is maintained as long as the knobs are adjusted to the same number of degrees. It is also possible to obtain the desired constant ratio between inhalation and exhalation time by letting the two constrictions 183 and 20 be fixedly adjusted. In this case, the variation of the breathing frequency that may be desired in some cases can be obtained by letting the volume of the chamber 19 be variable, for instance by connecting this chamber with an additional chamber of adjustable volume.

Between the conduit 16 and the conduit 2 leading to the patient there is inserted a valve mechanism 24, which causes the quantity of breathing gas applied to the patient to have a constant value even if the resistance presented by the patients breathing organs or by the passages connecting therewith should vary. The mechanism 24 for this purpose comprises a valve 25 having a variable constriction action. The valve 2 comprises a needle 26 connected with a membrane 27 adapted to move the needle towards and away from the valve seat. The one side of the membrane forms a wall of a chamber 28, which is directly connected through a conduit 29 with the conduit 2 leading to the patient. This causes the pressure in the chamber 28 to be always equal to the pressure in the conduit leading to the patient. The membrane 27 is further subjected to the pressure of a spring 30, which can be made to press more or less strongly against the membrane 27 with the aid of an adjustment screw 31. On the other side of the membrane, there is a second chamber 32, which is connected with the surrounding atmosphere through a non-return valve 33 on the one hand and through a passage 34 of variable area on the other hand.

An adjustment of the minimum quantity of air that may pass through the valve 25 under ordinary conditons is provided in the form of an arrangement for limiting the movement of the valve towards its seat. For instance, as shown in the FlGURE, the needle 26 may be provided with a flange 69, which during the movement of the needle against the valve seat abuts an adjustment screw 61, whereby the movement of the valve needle towards its seat is limited.

The gas applied through the conduit may be the only breathing gas applied to the patient. However, a saving of gas may be obtained by means of an injector 35 inserted between the valve and the conduit 2 and by means of which air may be sucked in from the surrounding atmosphere, whereby some saving in gas applied through the conduit 15 is obtained. In the air intake from the atmosphere, there is inserted an air filter 36 and a valve 37 of adjustable cross-sectional area. By means of this valve 37, the quantity of air which is applied to the patient from the surrounding atmosphere may be adjusted to a desired value.

By means of the adjustment screw 31, the influence of the spring on the membrane may be adjusted in 611 a way that during normal conditions a predetermined quantity of air passes through the valve 25 for each inhalation. If then for some reason or other, the resistance should increase for instance in the patients breathing organs or in the conduit 2-, the pressure increases in the conduit 2 and therefore also in the conduit 29 and the space 28. The membrane 27 is actuated by this pressure, so that the valve needle 26 is removed somewhat from its valve seat, whereby an increase in the quantity of gas passing through the conduit 16 is obtained. This increase may be large enough to compensate exactly the decrease in the amount of breathing gas applied to the patient caused by the increased resistance in the said conduits. The device may also be controlled in such a way that the pressure exerted by the spring 30 on the membrane 27 is varied by means of the adjustment screw 31 in such a way that either an incomplete compensation or an overcompensation is obtained. In the latter case, there is obtained an increase in the amount of breathing gas supplied to the patient owing to the increased resistance in the said conduits.

When the membrane 27 is actuated in the manner described by the increased pressure in the chamber 28, air is forced out of the chamber 32 into the surrounding atmosphere through the non-return valve 33, which then closes. At the subsequent decrease in pressure in the conduit 29, air is sucked into the chamber 32 at a rate determined by the constriction in the channel 34. This delays the return function, so that the valve 25 is prevented from oscillating in synchronism with the breathing. Such a delay can also be obtained by inserting a non-return valve in the conduit 29, which would allow the gas to be forced swiftly into the chamber 28, this non-return valve being then in parallel with a conduit having a constriction which allows the pressure within the chamber 28 to decrease slowly.

In the embodiment of the invention shown in FIG- URE 2, the conduit 2 is assumed again to be connected to the patient for applying breathing gas. The breathing gas is inducted into the device through an intake 38 and passes through a valve 39, the area of which is adjustable, and through a non-return valve 40 to be collected in a rubber bag 41, from which it can be forced into the conduit 2. The compression of the rubber bag 41 is obtained by means of a surrounding chamber 42, which is connected through a conduit 43 with a pulsating-pressure source not shown on the drawing. This source may consist, for instance, of a reciprocating piston. The breathing gas inducted through the intake 38 may, as before, be air or oxygen, possibly with an admixture of a narcotic gas. There is also provided a second intake 44 for breathing gas in the form of a valve having an adjustably variable flow resistance. This valve is constructed so as to allow an increased supply of breathing gas to the bag 41 and thus to the conduit 2 when the resistance presented by the patients breathing organs increases. To this end, the valve 44 is actuated by a membrane 45 forming a wall of a chamber 46. The chamber 46 is connected to the conduit 2 via a nonreturn valve 47 and a connection 48 provided with a variable constriction. The valve 44 is also influenced by a spring 49, whose pressure against the valve 44 can be adjusted by means of an adjustment screw 50.

The device shown in FIGURE 2 operates as follows: It will be assumed first that the breathing resistance in the breathing organs of the patient is normal and that an inhalation has just been completed. The exhalation is brought about owing to the pressure decrease in the chamber 42, which causes the rubber bag 41 to expand. Breathing gas is then inducted through the non-return valve 40 and through the valve 39 at a rate determined by the adjustment of the latter valve. The then following pressure increase in the chamber 42 causes the rubber bag 41 to be compressed, whereby the breathing gas in this bag is forced into the conduit 2 and on to the patient. If for some reason or other, the breathing resistance in the patlents breathing organs should increase, this. might lead to an increased fraction of the breathing gas being compressed in the conduit 2 without being supplied to the patient, which thus causes the ventilation of the patient to be insufiicient. This decrease in ventilation is made up for in the FIGURE 2 device owing to the fact that the increase in pressure created in the conduit 2 is able to raise the non-return valve 47 so that a certain amount of gas is forced into the chamber 46. This causes the valve 44 to be raised by the membrane 45 so that upon a sub sequent pressure decrease in the chamber 42 with the consequent expansion of the rubber bag 41 a still larger amount of gas can be inducted into it, since the breathing gas is supplied not only through the intake 38 but also through the valve 44. By means of the spring 49 and the adjustment screw 50 this extra amount of gas can be adjusted for full compensation, undercompensation or overcompensation of the decrease in ventilation caused by a possible resistance in the patients breathing organs. Similarly to the FIGURE 1 device, the non-return valve 47 and the connection 48 serve to delay the return to the original state to a desired extent.

As was mentioned in the introduction, the ventilation of the patient can also be held at a constant value if the ratio between inhalation and exhalation time is varied in dependence upon the pressure within the conduit leading to the. patient. For instance, an arrangement corresponding to the unit 24 of FIGURE 1 may be made to control either of the constrictions 18 and 20 of the unit 10 so as to increase the inhalation time in comparison with the exhalation time when the membrane 27 is actuated by an increased pressure in the conduit 2 that may be caused by an increased resistance in the patients breathing organs.

What we claim is:

1. Apparatus for supplying breathable gas to a patient comprising a source of breathable gas, conduit means for conducting said gas to the lungs of a patient, means for creating a pulsating flow of gas through said conduit, and pressure responsive means for increasing the flow of gas through said conduit during each pulse when an increase in flow resistance causes an increased pressure in said conduit.

2. Breathing apparatus for a patient comprising a source of breathable gas, conduit means for conducting said gas to the lungs of a patient, means for creating a pulsating flow of gas through said conduit, valve means in said conduit for controlling the flow of gas, pressure responsive means opening said valve means upon an increase in pressure in said conduit, said pressure responsive means including a chamber divided into two compartments by a flexible diaphragm, one of said compartments being connected to said conduit between said valve means and the patient and the other of said compartments communicating With atmosphere, and means connecting said diaphragm to said valve means, whereby an increase in pressure in said conduit causes an increase in the flow of gas.

3. Apparatus according to claim 1 wherein said means for creating a pulsating flow of gas through said conduit includes a member of variable volume.

4. Apparatus according to claim 2 wherein said compartment communicating with the atmosphere does so through a non-return valve and a passage of adjustable area.

References Cited in the file of this patent UNITED STATES PATENTS 501,959 RaWlingS fluly 25, 1893 2,408,136 FOX Sept. 24, 1946 2,737,178 POX Mar. 6, 1956 2,766,753 Koch Oct. 16, 1956 2,904,034 Haupt Sept. 15, 1959 

1. APPARATUS FOR SUPPLYING BREATHABLE GAS TO A PATIENT COMPRISING A SOURCE OF BREATHABLE GAS, CONDUIT MEANS FOR CONDUCTING SAID GAS TO THE LUNGS OF A PATIENT, MEANS FOR CREATING A PULSATING FLOW OF GAS THROUGH SAID CONDUIT, AND PRESSURE RESPONSIVE MEANS FOR INCREASING THE FLOW OF GAS THROUGH SAID CONDUIT DURING EACH PULSE WHEN AN INCREASE IN FLOW RESISTANCE CAUSES AN INCREASED PRESSURE IN SAID CONDUIT. 